Recently, intelligent vehicles and smart cars require proactive coping functions of the vehicle against outbreak situations. That is, there is a need to ascertain in advance situations menacing safety of a driver or a pedestrian such as recognizing sudden appearance of a pedestrian, detecting in advance an obstacle in a place away from lighting scope in a dark night time, detecting an obstacle when illumination from headlamps is weak due to rainfall, or detecting in advance the road damage.
Scanners are developed to meet these demands, where the scanner is installed at a front side of a vehicle or a windshield to ascertain a front object, to warn a driver in advance that the object lies ahead, and to transmit to an ECU (Electronic Control Unit) of the vehicle a basic image for the vehicle to stop itself or avoid the object, whereby the ECU performs various controls using the image thus obtained. The scanner may also mean a device for obtaining the image.
A RADAR (Radio Detection and Ranging) device has been conventionally used for the scanner. The radar is a radio detection device in which an electromagnetic wave of microwave level (ultrahigh frequency (e.g. approximately 1 cm˜10 cm wave) is emitted to an object and a reflected electromagnetic wave is detected and received to measure a distance, a direction and an altitude of the object. The RADAR has been used for a vehicle but disadvantages are that it has not been widely distributed or used for various types of vehicles due to high price.
In order to solve the disadvantages, a scanner using LiDAR (laser imaging detection and ranging) range-finding system has been developed. LiDAR is a distance range measurement technique for measuring distance or an atmospheric phenomenon in which a brief laser pulse (e.g. approximately 1˜10 nanoseconds pulse width) is emitted and the reflected light is detected while the time between the emitted pulse and reflected pulse is measured, which is also called a laser RADAR. Time measurement of reflected light is calculated by clock pulse, and the LiDAR has a resolution of 5 m for 30 MHz and 1 m for 150 MHz in the number of vibrations.
Currently, although 360° LiDAR scanner has been developed as a LiDAR mounted on a vehicle, which scans surroundings by allowing a body of the LiDAR to rotate 360°. As a result, a configuration of supplying an electric power to a rotating body must be essentially provided and an electrical rotary joint is a must for transmitting the electric power.
As noted from the foregoing, the conventional 360° LiDAR scanner must include a physical contact structure in order to transmit the electric power to the rotating body, whereby there was generated a problem of durability of optical system itself and reliability of scanned data. Furthermore, price of electrical rotary joint was relatively high and the 360° LiDAR scanner that essentially included the electrical rotary joint had a limit in price reduction.